Carrier-wave transmission system



Patented Nov. 6, 1923.

UNITED STATES Urattsman PATENT OFFICE.

ARTHUR W. KISHPAUGH, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED. OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

CARRIER-WAVE TRANSMISSION SYSTEM.

Application filed May 3, 1921.

To all whom it may concern:

Be it known that I. ARTHUR W. KrsH- PAUGH. a citizen of the United States of America. residing at East Orange. in the iounty of Essex and State of New Jersey. have invented certain new and useful Improvements in Carrier-Valve Transmission Systems. of which the following is a full, clear. concise. and exact description.

This invention relates to carrier wave transmission systems.

According to present practice in this art, high frequency oscillations are produced, controlled or modified in accordance with signals or impulses to be sent. and transmitted to a distant station. It is often desirable to be able to control the source of oscillations from a remote pointsuch as an operators switchboard. Particularly is this true in duplex radio transmission if the local radio transmitting and receiving apparatus are separated by a considerable distance and the operators position is at the receiving apparatus or any other point remote from the transmitter. A feature of this invention is a remote control of the source of high frequency oscillations.

In radio systems of the type described, it is highly desirable for the operator at the remote posit-ion to know if the radio transmitting system is functioning properly and accordingly whether the transmitting antenna is being supplied with radio frequency current of the proper frequency. An additional feature of the invention consists in an indicator for showing the presence in the transmitting antenna of radio frequency current of the proper frequency and for giving an alarm at the transmitter station when this current fails or materially changes frequency.

The ordinary three-element electric discharge device having a cathode. an anode, and an impedance control element requires a sour. e of heating current for the cathode and a source of space current. If the full working voltage of the space current source be applied to the electrodes of the device before the cathode is heated and if the magnitude of the space current be large it may result in damage to or destruction of the discharge device; A feature of the present invention is the provision of means for safeguarding such a device against high, space current a considerable distance.

Serial No. 466,477.

radio receiving apparatus and radio transmitting apparatus separated therefrom by An operator at the receiving apparatus is provided with facilities for connecting the system to signal lines to permit carrier Wave transmission of signals originating in these lines. The transmitting apparatus consists of an electric discharge oscillator of well-known type having direct current generators for supplying cathode heating current and space current. The apparatus at the operators position includes a switch to open and close the circuit of a remote relay which controls the field of the cathode heating current generator. This generator in turn sup-plies field current to the space current generator. A time-limit relay energized from the cathode heating circuit or the space current circuit serves to delay application of the full voltage of the space current generator and to reduce the space current of the electric discharge device until its cathode has had time to become fully heated. When the electric dischargeoscillator is fully in operation, it supplies radio frequency oscillations to a radio transmitting antenna. A circuit is coupled to this antenna to abstract a small portion of the energy supplied thereto in order to control an indicator at the remote operators position. thus enabling the operator to ascertain whether or not the transmitting antenna is in operative signal transmitting condition.

The novel features which are considered characteristicof the invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation together with further objects and advantages thereof will best be understood by reference to the following description taken in connection with the accompanying drawing in which Figure 1 shows diagrammatically a circuit arrangement which may be employed in carrying the invention into effect and Figure 2 shows a modification of a detail of Fi ure 1.

Referring to figure 1, a plurality of signal lines 1 terminating at the ordinary tele.

phone exchange are associated with the signal circuit 2 of a carrier wave transmission system. The receiving apparatus of the carrier wave transmission system indicated generally by R is shown at the left of the broken line C The transmitting apparatus designated generally by T is shown at the right of this line. The receiving apparatus comprises a receiving antenna 3 preferably tuned to the wave length of the carrier waves which it is desired to receive, the demodulating apparatus 1 for demodulating the received waves to produce the desired signal, and a filter 5 for transmitting the demodulated signal currents with negligible attenuation while substantially suppressing currents of other frequencies. The signal circuit 2 is terminated at the operators position in a balancing network N for simulating its impedance and that of the average circuit 1 or other circuit connected thereto at the frequencies of all currents to be transmitted over circuit 2. The incoming channel 6 from the radio receiving apparatus and the outgoing channel 7 leading to the radio transmitting apparatus are conjugately connected to the signal circuit 2 by means of the hybrid coil or balanced transformer 8 in well-known manner. The outgoing channel 7 includes a filter 9 similar in every respect to filter 5.

The transmitting apparatus comprises an oscillator O, a variable inpedance device M, and the thermionic amplifier A. The oscillator includes two electric discharge devices -10 connected in parallel and each having the usual cathode, anode and impedance control element. The alternating current output circuit of the devices 10 may be traced from their anodes by way of condenser 11 and primary winding 12 in parallel, and condenser 14, to the cathodes. Primary winding 12 is inductively coupled to secondary winding 13 included serially in the circuit of transmitting antenna 15. The primary winding 16 also included serially in the antenna circuit is inductively coupled to secondary winding 17 and Serves to feed back oscillations from the antenna circuit to the alternating current input circuit of devices 10 which includes winding 17 and capacity element 18 in series. An inductometer winding 19 enables variation of the tuning of the antenna 15 which serves as the frequency determining circuit for the oscillator. The variable condenser 11 serves to so change the constants of the interior circuit as to prevent oscillations .therein. The interior circuit comprises winding 17, condenser 18, condenser 14, elements l1 and 12 irf parallel and the inherent capacity between the anodes and control elements. Condenser 11 therefore serves to prevent the absorption of power by interior oscillations. It further serves to improve the power factor of the plate current. in a measur compensating for the leakage reactance ot' the winding 12. Modulation is accomplished by means of the constant current system of R. A. Heising fully disclosed at page 360. Proceedings of A. I. E. E., Volume 38, No. 3. The variable impedance device M comprises two electric discharge devices 20 connected in parallel. A generator (i having a separately excited field winding F B supplies space current to devices 10 and 20 in parallel over a path including constant current choke 21. inductance 22. automatically operating circuit breaker 23. and left-hand blade of switch 24: to the positive terminal of generator (i From the negative terminal of this generator. the space current path may be traced by way of the rightliand blade of switch 24, series inductance resistance 26, and resistance 27 to the cathodes of devices 10 and Connected in shunt across the space current circuit are capacity elements 39, which in conjunction with series inductances 22 and 25 serve to prevent commutator ripples and other fluctuations in the voltage of source G from affecting the space current and also serve to prevent high frequency oscillations from being impressed upon the generator G through the space current circuit. Filament heating current is supplied by a generator G having a series field winding F and a shunt field winding F In series with the shunt field winding is a variable resistance 28 and a high resistance 29 which directly across the output terminals of gen-- erator G to be supplied with exciting current therefrom. A switch 32 is interposed in the filament heating circuit to enable this circuit to be opened when desired. The input circuit of thermionic amplifier A is coupled by a transformer 33 to theoutgoing channel 7. The secondary winding of the transformer is shunted by a resistance 34 to improve the impedance characteristic of the transformer 33 in well-known manner. Amplifier A is supplied with cathode heating current from source G and is supplied with space current by source G over a path identical with that for devices 10 and 20 except that instead of passing through the constant current choke 21, the space current for the amplifier traverses a resistance 35 to reduce the effective voltage impressed across the electrodes of the amplifier. Resistance 35 is shunted by a capacity element 36 to reduce the impedance of the output circuit of the amplifier for the amplifier signal currents. A transformer 37 couplesthe output circuit of amplifier A with the input circuit of variable impedance device M. A resistance 38 which may be of the order of 10.000 ohms and therefore of small magnitude with respect to the input inpedance of devices 20 is included in shunt to the secondary winding of transformer 37 to stabilize the impedance connected to this winding. A radio frequency choke 40 which freely passes low frequency signal current serves to prevent radio frequency oscillations from being impressed upon and dissipated in the circuits of the variable impedance devic and the space current generator. The cathode of each electric discharge device is equipped with an individual regulating resistance 41 for varying the heating current.

The input circuit of amplifier A may be traced from the impedance control element of the amplifier through the secondary winding of transformer 33 to a point in resistance 26 and thence through the upper portion of this resistance and resistance 27 to the cathode. Since space current passes through resistances 26 and 27 there will be a potential drop between the cathode and the point in resistance 26 and the control element or grid of the amplifier will accordingly be maintained at a potential negative with respect to that of its cathode. The input circuit of discharge devices 20 is connected to the lower terminal of resistance 26 and their impedance control elements are accordingly maintained at a potential still more negative than that of the control elements of the amplifier. The grid leak path of the oscillator includes a resistance element l2 connected to the upper terminal of resistance 26 and the control elements or grids of the oscillator are maintained at a less negative potential determined by the potential drop across resistance 27 in consequence of the space current flowing therethrough. The grids of the amplifier, variable impedance device and oscillator are accordingly each maintained at such negative potentials with respect to their individual cathodes as to reduce their respective space currents to extremely small values. Oscillations are not produced under these conditions. A time-limit relay 43 is connected across th terminals of enerator G This relay when energized c oses its normally open contacts -14 to short-circuit resistance 27. As soon as resistance 27 is shortcircuited the grids of the various discharge devices become less negative and permit more space current to flow. thus rendering each of the devices operative and causing radio frequency oscillations to be produced in the antenna. This action is further in creased by the reduction of the external resistance in the space current circuit when resistance 27 is short-circuited, in effect increasing the effective space current voltage.

Draftsmau In order to prevent surges in the space current circuit in consequence of opening or closing of contacts 44, a path including a resistance 45 and a capacity element 46 in series therewith is shunted across the terminals of resistance 27.

Connected serially in the antenna circuit is the primary winding -18 of a transformer 4.9 to which is connected a rectifying electric discharge device 50 comprising a thermionic cathode and an anode. A portion of the secondary winding of transformer T9 is connected to the terminals of the cathode to supply heating energy thereto and the remainder of this winding is connected across the cathode and anode to supply rectified energy to a relay 51 in series therewith. Relay 51 is provided with an armature 52 controlling a circuit 53 which is simplexed over a talking circuit 54 extending from the radio transmitting apparatus to the operators position at the radio receiving apparatus or elsewhere. The circuit 53 includes a relay 64 grounded through battei'y at the operator's position and serving by means of its armature 55 to control the energization of the signal lamp 56. Armature 52 also controls a circuit which includes a current source 66, a bell or other alarm 57 and which is open at the normally open upper contacts of time limit relay 43. This alarm is therefore actuated whenever relay 43 is energized and relay 51 is not energized. Telephone sets 58 of conventional design are shown associated with talking circuit 5st to permit communication from the operators position to the transmitting station without recourse to outgoing channel 7.

A switch 59 in circuit 60 at the operators position permits the remote control of relay 31. The generators G and G are directly connected or driven in any suitable manner by a constantly acting device 61 shown as a three-phase alternating current motor.

Figure 2 illustrates a modification of the arrangement for controlling indicators 56 and 57 at the operators position and radio transmitter respectively. According to this modification, the secondary winding of transformer 49 is included with a variable capacity 62 in a closed tuned circuit such as is ordinarily used in wave-meter circuits. This circuit also includes a thermo-couple 63 which may be connected to the relay 51 to supply an energizing E. M. F. thereto.

The operation of the circuits described may now be explained. As illustrated the alternating current motor 61 is in operation and generators G and G are operating at full speed. Resistance 29 in the shunt field circuit of generator G prevents this generain the antenna 15 and relay 51 is deenergized and indicators 56 and 57 indicate this condition at the operators position at the. receiving apparatus and at the ratio transmit-- ter respectively. If the operator receives a call either over the radio receiving apparatus 3. l. 5 or over one of the signal lines 1, or for any reason whatever desires to put the radio transmitting apparatus in operative condition. it is merely necessary to close switch 59. Relay 31 will then he energized pulling up armature 30 to short-circuit resistance 29 and permit generator G to build up its voltage. Generator G will thereupon supply heating current to the cathodes of each of the electric discharge devices, energizing current to the time-limit relay l3, and field current to generator G Generator G thereupon builds up its voltage and supplies space current through resistances 26 and :27 to each of the electric discharge devices. After suflicient time has elapsed to permit the cathodes to become fully heated, time-limit relay 43 operates to close contacts i-t, short-circuiting resistance 27. This decreases the normal negative potential on the grids or control elements of the amplifier and discharge devices 10 and 20 and permits full magnitude space current to flow through each of these devices. The oscillator thereupon produces radio frequency oscillations in the antenna 15 and a portion of this radio frequency energy is supplied by a transformer 49 through the rectifier 50 or the thermo-couple 63, as the case may be, to operate relay 51 and thus give an indication at the operators position that the transmitting apparatus is in operative condition. The operator noting this indication may now make the necessary connections for duplex radio signaling.

The modification of Figure 2 presents the added advantage that the indicators 56 and 57 show not only the presence of radio frequency current in the antenna, but also indicate that this current is of the proper frequency. If for any reason the supply of radio frequency oscillations to the antenna fails the alarm 57 will immediately show this at the transmitter position and if the modification of Figure 2 including the circuit 49, 62. 63 tuned to the desired carrier frequencybe used, the alarm will indicate not only failure of radio power in the antenna, but also any marked change in frequency.

The time-limit relay 43 may be any type of slow acting element and it may be connected in various other ways without departing from the spirit of the invention. For example its operating or energizing winding may be connected in shunt to resistance 26 instead of across the filament heating circuit as illustrated or it may be inserted directly in series in the space current circuit between the points or 71. In this case the relay need not be slow acting since the time element is given by the time required for the space current itself to build up to suificient value to energize the relay.

Although the features of the invention have been described and illustrated as embodied in a specific radio system, it is to be understood that they are not to be restricted thereto. Obviously the receiving and transmitting antenna may be replaced by conductive carrier wave circuits. Moreover, certain of the features of the invention are capable of use generally without regard to signal transmission.

What is claimed is:

1. In combination, means for transmitting high frequency waves, generators for supplying energy thereto, a control station re-.

mote from said means, said control station having means for controlling said generators to render said transmitting means active.

2. An oscillator comprising an electric discharge device having a thermionic cathode and an anode, a generator for supplying space current to said device, a second generator for supplying heating current to said cathode and exciting current to the field of said first generator, a remote control station and means at said station for controlling the energization of said second generator.

3. A radio system comprising radio transmitting apparatus, a signaling line for connecting said system with a subscribers sta tion for communication by said subscriber through said transmitting apparatus, power sources therefor, an operators station remote from said transmitting apparatus, means at said operators station for controlling the connection of said power sources to said transmitting apparatus to render the transmitting apparatus active.

4. A radio transmitting station comprising a vacuum tube oscillator having a cathode and an impedance control element, local generators connected respectively to said cathode and to said cathode and anode for supplying cathode heating current and space current, a constantly energized motor directly connected to said generators for supplying mechanical energy thereto, a remote control station and means thereat for controlling the excitation of said generators.

5. An electric discharge device having two electrodes one of which is a thermionic cathode, a high voltage generator for supplying space current to said electrodes, a low voltage generator for supplying heating current to said cathode, a field winding for said low voltage venerator, a resistance in series therewith of such magnitude as normally to prevent excitation of said low voltage generator, a field winding for said high i-A-NLENE ass-.1 RG

voltage generator connected across the output terminals of said low voltage generator, :1 remote control station, and means at said remote control station for short-circuiting said resistance to enable said low voltage generator to be excited.

6. A high frequency transmitting station comprising a source of oscillations and a high frequency transmission conductor, a remote control station having an indicator and means associated with said transmission conduotor and controlling said indicator to indicate the presence in said conductor of oscillations of a desired frequency in combination with a main signaling channel connecting said transmitting station and said remote control station.

7. A high frequency station comprising a source of oscillations, a high frequency transmitting conductor associated therewith, a remote control station, a rectifier coupled to said antenna, and an indicator at said remote control station controlled by said rectifier to indicate the presence of oscillations in said antenna in combination with an alarm device at said high frequency station to indicate failure of said rectifier.

8. A radio transmitting station comprising an oscillator and a radiating conductor associated therewith, a tuned circuit coupled to said conductor, a remote control station, a visual indicator thereat, and means controlled-by said tuned circuit for operating said 'fndicator to, indicate the presence in sai conductor of oscillations of a desired quency.

9. A radio transmitting station comprising 'a transmitting antenna, means for supplying high frequency oscillations thereto, a remote control station, means other than s'gna ng mec anism at said remote control station, for controlling said supplying means, and means at said remote control station to indicate the presence of high frequency oscillations in said antenna prior to and during the transmission of signals.

10. A radio system comprising radio transmitting apparatus, power sources therefor, an operators station remote from said transmitting apparatus, means at said operators station independent of means for transmitting through said apparatus for controlling the connection of said power sources to said transmitting apparatus to render the transmitting apparatus active, an antenna energized by said transmitting apparatus, and means at said operators station for indicating energization of said antenna.

11. A radio system comprising transmitting apparatus and receiving apparatus, an operators station, conductive signaling lines terminating at said operators station, means at said station for connecting any of said lines to said transmitting and receiving ap- Draftsman paratus, a source of radio frequency power for said transmitting apparatus, and means at said station for indicating the operative ndition of said source of power.

Zll2. A radio system comprising it- 't g and receiving apparatus, a central operators station remote from said transmitting apparatus, a power source at said transmitting apparatus, a telephone line extending from a point adjacent said transmitting apparatus to said station, and means associated with said line for indicating at said station the operative condition of said transmitting apparatus.

13. An electric discharge device having a thermionic cathode and an anode, means for supplying heating current to said cathode, a source of space current for said device, and means for delaying the application of the full E. M. F. of said space current source to said device until said cathode has become energized.

14. A thermionic discharge device having two electrodes one of which is a thermionic cathode, a source connected to said cathode for supplying heating current thereto, a second source connected to said electrodes to supply space current thereto, a time limit relay havin normally open contacts in series in sai space current circuit andhaving an energizing winding connected to said filament heating source whereby the application of the space current source may be delayed for atime after the application of said filament heating source.

15. A thermionic discharge device having a filamentary cathode and an anode, a circuit connecting said cathode and anode and including normally open contacts and a source of space current in series, means for supplying heating current to said cathode and a slow acting relay connected in shunt to said cathode and provided with means for closing said contacts when energized.

16. A thermionic oscillator having a cathode, an anode and an impedance control element, a source of space current therefor, a resistance connected to the negative pole of said source and in series with the cathode-anode discharge path of said oscillator, a connection from the negative terminal of said resistance to said impedance control element, a switch for short circuiting said resistance and a path in shunt to said resistance and including capacity and resistance in series.

17. An electric discharge device having a cathode, an anode and an impedance control element, a source of space current having its positive terminal connected to said anode, and its negative terminal connected through two resistances in series to said cathode, a conductive connection from said impedance control element to the point intermediate to said series resistances wheresaid time limit relay to short-circuit a portion of the series resistance adjacent said cathode to cause said control element to become less negative with respect to said cathode.

In witness whereof, I hereunto subscribe my name this 2nd day of Ma A. D., 1921.

ARTHUR W. KI PAUGH. 

